| Summary: | 碩士 === 大同大學 === 材料工程學系(所) === 102 === Ba2MgWO6 (BMW) is a double perovskite-structured dielectric ceramic with high quality factor (Q). However, its sintering temperature reaches as high as 1575 ℃, which could not meet the requirements of ceramic multilayer technology. In addition, this ceramic forms BaWO4 phase when the temperature is over 1400 ?aC. The BaWO4 phase will degrade the dielectric properties and lower Q values of BMW. In order to alleviate these problems, we doped Sr to partly substitute Ba on one hand and added B2O3, 2Bi2O3‧B2O3, Bi2O3‧CuO, 3ZnO‧B2O3 and Li2O as sintering aids to lower sintering temperature on the other. Results of Ba2-xSrxMgWO6 (x = 0.0, 0.5, 1.0, 1.5) showed that when x=0.5 (i.e., Ba1.5Sr0.5MgWO6 ) Qxf value reached maximum. Further increase of Sr doping decreased Qxf value. The Sr doping had no significant changes in the dielectric constant εr while temperature coefficient of frequency drift τf increased from -27.7 ppm / ?aC to 24 ppm /?aC. For Ba1.5Sr0.5MgWO6 Qxf value was 152,603 GHz, dielectric constant εr was 20.6 and temperature coefficient of resonance frequency drift τf was 24 ppm/ ?aC. The addition of B2O3 had significant effect on the sintering of BMW. The sintering temperature decreased from 1575 ℃ to 1150 ?aC with 0-5 wt% of B2O3 addition. But when B2O3 addition was more than 2 wt%, the samples would exhibit substantial decrease in the Qxf value. Although 2Bi2O3‧B2O3, Bi2O3‧CuO, 3ZnO‧B2O3 and Li2O addition to BMW effectively reduce the sintering temperature, Qxf value is greatly reduced. The best conditions was to add 2wt% B2O3. The sintering temperature of BMW-2 wt% B2O3 dropped to 1350 ?aC. Its Qxf value could reach 138,595 GHz. The dielectric constant was 16.6 and the temperature coefficient of resonance frequency drift was -11 ppm /?aC. When Ba1.5Sr0.5MgWO6 was added with 2wt% B2O3 the sintering temperature was further lower from 1400℃ to 1200?aC, but the Qxf becomes low.
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